Friday, September 16, 2005

Possible Oregon volcano could be a threat or not

Because it lies far from heavy populations, Crater Lake receives the least monitoring for possible volcanic activity, even though it is considered one of the five most active volcanoes in Oregon.
"Crater Lake is the worst-case scenario," said seismologist Seth Moran of the U.S. Cascades Volcano Observatory in Vancouver, Wash. "Mount St. Helens taught us that we need a decent network of seismic monitors or else we might miss the subtle signs (of volcanism). Once they wake up, they’re too hot to get close to."

Although there is a network of seismic monitors up and down the Cascades, the nearest one to Crater Lake is 29 miles away. Two are distant to the west, one in Klamath Falls and a couple far to the south, he said.

"That speaks for itself," said Moran. "In every case, volcanoes have a monitor within five miles, but Crater Lake is a remote volcano, not near any town and it hasn’t erupted very recently. To be frank, resources are limited, so we have to concentrate on the most likely ones — Rainier (near Seattle), Hood (near Portland) and South Sister (near Bend)."

Moran said money is lacking for personnel and for purchase and maintenance of equipment that would form part of the monitoring network that relays data in real time.

"Crater Lake is suffering not for lack of interest but because it’s a good distance from Vancouver (location of Cascades Volcano Observatory) and because we’re forced to make cutbacks," Moran said.

However, he added, Crater Lake is at the point in its cycle where it would wake up by venting lava and building itself back up, rather than exploding.

The five volcanoes most likely to become active are Hood, Jefferson, South Sister, Newberry and Crater Lake. The latter made the list because it blew violently only 7,500 years ago, and Wizard Island, the volcanic cone within the caldera that holds the lake, blew only 5,000 years ago. South Sister, Hood and Newberry, all in the Central and Northern Oregon Cascades, have all erupted more recently.

Seismic monitors at Dodson Butte and Butler Butte, about 30 miles west of Crater Lake, and also in Klamath Falls, reliably monitor the national park down to 1.5 on the Richter scale, said Moran.
For scientists working at the park, volcanic activity is a thing of the far distant past or future.
Park historian Steve Mark said, "We used to have a monitor at the administration building here but the bouncing of traffic on the road above us would set it off, so it was removed."

Crater Lake was the most spectacular volcanic event in local human memory when it exploded violently, leaving a huge caldera that filled with rain and snowmelt and is now among the purest natural water on earth. The event is recalled in the mythology of the Klamath Indians whose territory was hit by lava and ash.

Since then, said Mark, there have been only hints of Mazama’s power — gaseous clouds emerging from the waters through the summer of 1945 and magma-caused earthquakes up to 6.0 magnitude at nearby Mountain Lakes Wilderness Area in 1993.

These were associated with the Klamath Lake earthquake that damaged Klamath Falls and included 2,500 aftershocks over several months. That seismic swarm is not associated with Crater Lake, said Moran.

Although Crater Lake is called "the sleeping giant," "we haven’t had any indication that Crater Lake is active," said Mac Brock, chief of natural resources for the park. "A volcanic eruption is really highly unlikely. It’s not considered an area of concern like Mount Rainier — or like Mount Lassen, (a Northern California volcano that last erupted in 1915)."

Still, said Mark, it’s only a question of when. "Today it’s in the caldera stage (a water-filled crater). That will change."

If we could peep 10,000 years into the future, added Moran, "it wouldn’t surprise me if Mazama had erupted. (Mount Mazama is the ancient volcano that collapsed to form the Crater Lake caldera.) It could do big or small eruptions. Most volcanoes are like Mount St. Helens now, periods of gases and lava flows. Crater Lake is due to rebuild itself in time — and so it would be doing the flows, not the explosions."

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